1. Field of the Invention
The present invention relates to a laminated chip electronic component for reducing acoustic noise generated by the laminated chip electronic component, a board for mounting the same, and a packing unit thereof.
2. Description of the Related Art
A multilayer capacitor, a laminated chip electronic component, includes internal electrodes formed between a plurality of dielectric layers.
When DC or AC voltages are applied to the multilayer capacitor having internal electrodes overlapping with dielectric layers interposed therebetween, a piezoelectric effect takes place between the internal electrodes, generating vibrations.
As permittivity of a dielectric layer becomes higher and the size of a chip is larger based on the same capacitance, generated vibrations become more intense. The generated vibrations are transferred from external electrodes of the multilayer capacitor to a printed circuit board (PCB) on which the multilayer capacitor is mounted. Here, the PCB vibrates to produce a noise.
When the noise produced due to the vibrations of the PCB is included in an audio frequency, a corresponding vibrating sound may make users uncomfortable, and such a sound is known as acoustic noise.
In order to reduce acoustic noise, the inventors of the present invention have conducted research into a mounting direction of internal electrodes within a multilayer capacitor, in relation to a PCB. As a result of the research, it has been recognized that mounting a multilayer capacitor on a PCB to have directionality such that internal electrodes of the multilayer capacitor are horizontal with the PCB may reduce acoustic noise in comparison to a case in which a multilayer capacitor is mounted on the PCB such that internal electrodes thereof are perpendicular to the PCB.
However, even in the case that the multilayer capacitor is mounted on the PCB such that internal electrodes thereof are horizontal with the PCB, acoustic noise may be measured and determined to still be at a certain level or higher, so a further reduction in acoustic noise remains an issue to be studied.
[Prior Art Documents]    (Patent document 1) Japanese Patent Laid Open Publication No. 1994-268464    (Patent document 2) Japanese Patent Laid Open Publication No. 1994-215978    (Patent document 3) Japanese Patent Laid Open Publication No. 1996-130160
Patent document 1 discloses internal electrodes mounted to have horizontal directionality in relation to a PCB, but it has technical characteristics in which a pitch between signal lines is narrowed to reduce high frequency noise. Meanwhile, Patent document 2 and Patent document 3 disclose different thickness of an upper cover layer and a lower cover layer in a multilayer capacitor. However, the documents do not suggest any motive or solution for reducing the acoustic noise. Moreover, the documents absolutely do not disclose or anticipate an extent of how much the central portion of the active layer is deviated from the central portion of the laminated chip capacitor, a ratio of the upper cover layer to the lower cover layer, a ratio of the lower cover layer to the thickness of the ceramic body, and a ratio of the lower cover layer to the thickness of the active layer, etc.